a. Field of Invention
This invention pertains to a polyprismatic lens and, more particularly, to a lens having a plurality of parallel prisms. The power of the prisms is increased from a central portion of the lens towards the periphery. The lens is useful for enhancing the actual or apparent effect of eye movement of a wearer.
b. Description of the Prior Art
The motility of an eye (the ability of a person to move his/her eye) is frequently affected by various pathological causes such as extra-ocular muscle disease or by motor nerve innervational deficiency. Persons having this problem have in effect a reduced range of eye movement and have trouble directing the affected eye toward objects which do not lie directly in front of them. In most situations, these persons must turn their heads in order to bring the objects into their central vision. Furthermore, if this condition affects only one eye, the affected person's face and appearance becomes unsymmetrically and aesthetically displeasing. This latter factor is also applicable to people who lost an eye and must wear a prosthesis. Usually, because of either retained extra-ocular muscle dysfunction or cicatricial restrictive reasons, the prosthesis device may be hard or impossible to move beyond a small angle.
Until the present invention, there were no devices which could enhance small eye movement satisfactorily. For example, in U.S. Pat. No. 3,423,151, E.B. White discloses a pair of glasses with a prism secured to the frame for extending the field of vision of the wearer. However, this approach is useful only for a small number of patients because it requires the ability to look sideways. Furthermore, it does not improve the aesthetic appearance of the wearer.